Abstract:

The purpose of this thesis is to offer a critical review of existing and emerging recycling technologies for lithium ion batteries (LiBs), based on a literature research. Additionally LiBs as sources of secondary raw materials are described, and the current status and possibilities of mechanical processing methods in LiBs recycling is studied. Five industrial and four emerging technologies are analysed in detail based mainly on information provided by scientific articles and patents.

LiBs are used increasingly for providing energy to portable applications and electric mobility. The opera-tion principle of LiB is based on the layered active electrode materials that enable Li-ion insertion and transfer between the electrodes during discharge and charge. The performance and properties of LiB are especially dependent on the active cathode material. In present commercial LiB cells it consists of one of the five different compound types containing Co, Ni, Mn and Fe in different proportions, in addition to Li. Other materials in LiBs are graphite, Al and Cu foils, polymeric separator, electrolyte consisting of Li salt and organic materials, and the cell casing of stainless steel, Al or polymer. End-of-life batteries can have charge left, they can produce flammable and toxic gases, and they can contain flammable elemental Li – facts that have to be considered in recycling process.

In the studied technologies, mechanical, pyrometallurgical and hydrometallurgical techniques are utilized in different combinations for the recovery of LiB materials. Usually pyrometallurgical or mechanical treatment starts the process, followed by hydrometallurgical recovery of the cathode materials. Pyrometallurgical treatment loses Al and Li in slag but has the capability of treating mixed feed. In mechanical treatment, more materials can be saved but extra attention is needed for safe handling of the batteries: the batteries are discharged prior to crushing, and/or comminution is carried out in protective medium. The crushed materials are separated with magnetic (Fe, SS) and density based materials (Al, Cu, polymers), and differing particle size of particular materials. Combination of several crushing and separation steps or thermal treatment can be used for improved detachment of active cathode material from the foil which is crucial for the success of the recovery of cathode materials in the following hydrometallurgical treatment.

Only part of the once high-cost primary materials of the cell can be feasibly recycled to be used again. Co has been the driving force for recycling LiBs. Li is usually recovered in the end as a carbonate. For graphite and electrolyte recovery there exists methods, but the economic feasibility is questionable. Different organic materials have in general lost their value in the end-of-life of the cell. In some emerging technologies the goal is to produce cathode precursor material directly as an outcome of the mechanical and hydrometallurgical steps. This potentially saves more of the original cathode compound value, but requires also stricter processing conditions and control of the feed. Novel technologies consider the recovery other cathode compound materials than just Co, but are not able to treat the mixed cathode materials at the same time. Especially LiFePO4 is challenging material, because it has a low recycling value, and constitutes an impurity in the leaching process.Työssä analysoidaan teollisia ja orastavia litiumioniakkujen kierrätysteknologioita sekä mekaanisten prosessointimenetelmien asemaa ja mahdollisuuksia niiden osana. Analysoitavana on viisi teollista ja neljä orastavaa teknologiaa, ja tietolähteinä ovat pääasiassa tieteelliset artikkelit ja patentit.